In application Ser. No. 134,050, filed Mar. 26, 1980, now U.S. Pat. No. 4,318,531, issued Mar. 9, 1982 a tank car ball valve is disclosed and in application Ser. No. 134,231, filed Mar. 26, 1980, now U.S. Pat. No. 4,318,531, issued Mar. 9, 1982, a tank car cone valve is disclosed. These valves are located in valve housings located within the tank. The valves are rotated from below the tank by operating shafts which extend upwardly through outlet chambers and which engage the internal surface of the valves. Each of the valves contain inlet ports 180.degree. apart and an outlet port in the bottom of the valve through which the operating shaft passes.
However, the operating shaft passing through the outlet port and through the outlet chamber provides a flow restriction during lading discharge and during loading if loading occurs through the outlet valve.
Furthermore, in these constructions, the unloading spout is offset with respect to the axis of the outlet port and the spout extends a considerable distance below the tank bottom. This makes it difficult to attach an unloading conduit and/or an auxiliary unloading valve. The greater extension provides more liklihood than a non-offset, shorter arrangement for loss of the outlet chamber due to impact.
Furthermore, a considerable moment is generated because of the offset portion, particularly if an auxiliary valve is attached.
The center of gravity of the offset outlet chamber is located significantly below and to one side of the valve. The effects of impact and vibratory fatigue loads are thus magnified by the moment applied through this extended center of gravity.
The offset also makes it difficult to install a steam jacket.